Electrical switch construction and an electrical control system utilizing the same or the like

ABSTRACT

An electrical switch construction comprising a housing carrying a pair of movable spring switch blades respectively having contacts thereon that are normally placed out of electrical contact with each other by the normal bias of the switch blade. A pair of cams are rotatably carried by the housing and are respectively engageable with the switch blades, one of the cams when in one position relative to the housing being adapted to hold its respective switch blade in electrical contact with the other switch blade to complete an electrical circuit therebetween. The other of the cams when in one position thereof relative to the housing being adapted to hold its respective switch blade out of contact with the other switch blade even though the one cam is in its one position whereby the electrical circuit can not be completed. A movable actuator is carried by the housing and is adapted to simultaneously engage the cams and move the same to the respective one positions thereof whereby the switch construction is trip-free. A latch member is carried by the housing for holding the one cam in the one position thereof if the latch member is not tripped to an unlatching position thereof.

1 1 Nov. 12, 1974 ELECTRICAL SWITCH CONSTRUCTION AND AN ELECTRICAL CONTROL SYSTEM I UTILIZING THE SAME OR THE LIKE William J. Russell, Milford, Conn.

Robertshaw Controls Company, Richmond, Va

Filed: Dec. 14, 1973 Appl. No.: 421,525

Inventor:

Assignee:

US. Cl 337/64, 200/38, 219/265, 337/72, 337/82, 337/99, 337/101, 431/254 Int. Cl. H01h 71/16 Field of Search 337/52, 5557, 337/64, 70, 72, 75, 77, 82, 94, 99, 101, 103, 105; 219/260, 262, 264, 265; 200/38, 39; 431/254, 255, 258

References Cited UNITED STATES PATENTS Primary Examiner-Arthur T. Grimley Attorney, Agent, or Firm-candor, Candor & Tassone [57] ABSTRACT An electrical switch construction comprising a housing carrying a pair of movable spring switch blades respectively having contacts thereon that are normally placed out of electrical contact with each other by the normal bias of the switch blade. A pair of cams are rotatably carried by the housing and are respectively engageable with the switch blades, one of the cams when in one position relative to the housing being adapted to hold its respective switch blade in electrical contact with the other switch blade to complete an electrical circuit therebetween. The other of the cams when in one position thereof relative to the housing being adapted to hold its respective switch blade out of contact with the other switch blade even though the one cam is in its one position whereby the electrical circuit can not be completed. A movable actuator is carried by the housing and is adapted to simultaneously engage the cams and move the same to the re spective one positions thereof whereby the switch construction is trip-free. A latch member is carried by the housing for holding the one cam in the one position thereof if the latch member is not tripped to an unlatching position thereof.

20 Claims, 4 Drawing Figures 5 1 55 r2 t} 66 T9 \\\Ww 62 60073 38 ess ll ELECTRICAL SWITCH CONSTRUCTION AND AN ELECTRICAL CONTROL SYSTEM UTILIZING THE SAME OR THE LIKE This invention relates to an improved electrical switch construction as well as to an electrical control system utilizing such a switch construction or the like.

It is a feature of this invention to provide an electrical switch construction that is trip free.

It is well known in the art that safety electrical switches have been designed to be trip-free, i.e., a switch that must be manually reset after it has tripped to the open circuit condition after a fault in the circuit has been automatically detected and which at the same time cannot by means of the resetting means be held in a circuit closed position to thus negate the safety function of the switch. For example, see the US. Pat. to R- berts et a], No. 2,745,922.

Accordingly, it is a feature of this invention to provide an improved trip-free electrical switch of the above type.

In particular, one embodiment of this invention provides an electrical switch construction having a housing means provided with a pair of movable spring switch blades carried by the housing means and respectively having contact means normally placed out of contact with each other by the normal bias of the switch blades. A first cam is rotatably carried by the housing means and is engageable with one of the switch blades, the first cam when in one position relative to the housing means being adapted to hold its respective switch blade in electrical contact with the other switch blade to complete an electrical circuit therebetween. A second cam is rotatably carried by the housing means and is engageable with the other of the switch blades, the second cam when in one position thereof relative to the housing means being adapted to hold its respective switch blade out of contact with the other switch blade even though the first cam is in its one position thereof whereby the electrical circuit can not be completed when the cams are respectively in the one positions thereof. A movable actuator is carried by the housing means and is adapted to simultaneously engage the cams and move the same to the respective one positions thereof whereby the switch construction is tripfree. A latch member is adapted to hold the first cam in its one position thereof if the latch member is not moved to a tripped condition thereof. The actuator by being simultaneously engageable with both of the cams will move the cams in unison when the actuator is being moved from an unactuated position thereof to an actuated position thereof whereby the cams hold the switch blades in an open condition thereof when the actuator is in the actuated condition thereof. However, as the actuator is moved back to the unactuated condition thereof, both cams tend to follow such movement but the first cam will be latched by the latch member if the latch member is in a latching position thereof whereby the switch blades can be reset in electrical contact with each other. 7

Therefore, it is an object of this invention to provide an improved electrical switch construction having one or more of the novel features set forth above or hereinafter shown or described.

Another object of this invention is to provide an electrical control system utilizing such an electrical switch construction or the like.

Other objects, uses and advantages of this invention are apparent from a reading of this description, which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIG. 1 is a cross-sectional view of the improved electrical switch construction of this invention, the electrical switch construction being illustrated as being utilized in an electrical control system of this invention that is schematically illustrated in FIG. 1.

FIG. 2 is a view similar to FIG. 1 and illustrates the electrical switch construction in its tripped condition.

FIG. 3 is a fragmentary, cross-sectional view taken on line 33 of FIG. 1.

FIG. 4 is a view similar to FIG. 1 and illustrates the tripped electrical switch construction while an attempt is being made to reset the same.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted to provide an electrical switch construction that is trip-free, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide an electrical switch construction for other purposes as desired.

Therefore, this invention is not to be limited to only the embodiment illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, the improved electrical switch construction of this invention is generally indicated by the reference numeral 10 and comprises a housing means 11 carrying a pair of spring switch blades 12 and 13 respectively interconnected at the lower end thereof to terminal means 14 and 15 that project from the housing means 11 and carry at the upper ends thereof contact means 16 and 17 that are adapted to be placed in electrical contact with each other in the manner illustrated in FIG. 1 to complete an electrical circuit therebetween. However, the normal bias of such switch blades 12 and 13 is to tend to hold the contacts 16 and 17 out of electrical contact with each other in the manner illustrated in FIG. 2 so as to open the electrical circuit therebetween for a purpose hereinafter described.

The electrical switch constructionIO of this invention is adapted to be utilized in an electrical control system of this invention that is generally indicated by the reference numeral 18 in FIG. 1 and includes an electrically operated control device 19 which, in the embodiment illustrated in FIG. 1, comprises an electrical igniter means for igniting fuel when the same issues from a burner means 20 that has fuel directed thereto by a control device 21 which when turned to an on position thereof directs fuel to the burner means 20 as well as closes a main on-off switch 22 for the electrical circuit 18.

In particular, the main switch 22 of the electrical circuit 18 is adapted to open and close a switch member 23 in a power source lead 24 which is interconnected to the terminal 15 of the electrical switch construction 10. Thus, if the switch blade 23 is in an open condition, the power source L1 is disconnected from the terminal 15 and when the'switch blade 23 is in a closed condition the power source L1 is interconnected to the terminal of the switch construction 10. Similarly, the main switch 22 includes a switch blade 25 disposed in a lead 26 that is interconnected to one side 27 of the igniter 19 and to ground at the other end thereof, the igniter 19 is disconnected from the ground and when the switch blade 25 is in a closed condition thereof the igniter 19 is interconnected to ground.

The other side 28 of the igniter 19 is interconnected by a lead 29 to the terminal 14 of the electrical switch construction 10. v

In this manner, when the switch blades 12 and 13 are disposed in the closed condition illustrated in FIG. 1 and the operator turns the control device 21 to an on condition thereof, the main on-off switch 22 closes the switch blades 23 and 25 in their respective lines 24 and 26 and the igniter 19 is placed across the power source L1 and ground whereby the ingiter 19 will be operating in an attempt to ignite fuel now issuing from the burner since the control device 21 has been moved to an on condition thereof to also direct fuel to the burner 20.

However, the electrical switch construction 10 of this invention is so constructed and arranged in a manner hereinafter set forth that should a sensor 30 of the system l8 detect that the burner 20 has not been ignited within a certain time period, the sensor 30 will, in effect, cause the electrical switch construction 10 to be tripped to the open condition illustrated in FIG. 2 and thereby terminate the operation of the igniter 19 until the switch construction 10 is manually reset from the open or tripped condition illustrated in FIG. 2 back to the closed position illustrated in FIG. 1 in a manner hereinafter described.

A bimetallic'latch member is disposed in a chamber 32 of the housing means 11 and has an L-shaped end 32 interconnected to a flexure member 33 that is fixed to the housing means 11 by a fixed support 34, the other end 35 of the bimetallic latch member 31 being turned over in such a manner that the same is adapted to engage against an angled surface 36 of a first cam 37 rotatably mounted to the housing means 11 by a shaft 38 carried by the housing means 11.

The cam 37 is so constructed and arranged that the same has a part 39 adapted to engage against the spring blade 12 and bias the same to the right in the manner illustrated in FIG. 1 when the cam member 37 is disposed in the position illustrated in FIG. 1 so as to maintain the contact 16 of the blade 12 into full electrical contact with the contact 17 of the blade 13 as such position-of the cam 37 not only biases the blade 12 to the right, but such position of the cam 37 also biases the blade 13 to the right so that the blade 13 is always spring biased against the contact 16 of the blade 12 when the cam 37 is in the latched position illustrated in FIG.'1. Because the spring blades 12 and 13 are tending to rotate the cam 37 in a clockwise direction in FIG. 1, the turned end 35 of the latch 31 prevents such movement of the cam 37 so that the cam 37 is latched in the position illustrated in FIG. 1 maintaining an electrical circuit between the switch blades 12 and 13 for the purpose previously described.

However, the bimetallic latch member 31 is adapted to be warped to the left to move the latching end 35 thereof out of the path of the surface 26 of the cam 37 when the bimetallic member 31 is heated to a certain degree by an electrical heater 40 that is carried by the bimetallic latch member 31 and has one end 41 thereof electrically interconnected by a lead 42 to a terminal 43 of the housing means 10. The other end 44 of the electrical heater 40 is interconnected by a lead 45 to a fourth terminal 46 of the housing means 11.

The terminal 46 is adapted to be interconnected by a lead 47 to ground while the terminal 43 is interconnected by a lead 48 to one side 49 of the sensor 30 while the other side 50 of the sensor 30 is interconnected by a lead 51 to the terminal 15.

In this manner, when the igniter 19 is initially turned on by the main on-off switch 22 being moved to a closed position by the control device 21 being turned to an on condition thereof, electrical current is adapted to flow not only through the sensor 30 but also through the electrical heater 40 whereby the electrical heater 40 begins to heat up the latch member 31 to tend to warp the same to the left and thereby open the electrical circuit being provided by and through the switch blades 12 and 13 for the igniter 19. However, if the operating igniter 19 during such time period ignites the burner 20, the sensor 30 senses such flames at the burner 30 and disconnects the electrical circuit through the sensor 30 so that the electrical heater 40 is disconnected from the power source Ll whereby the latch member 31 will remain in its latched position as illustrated in FIG. 1 to maintain an electrical circuit through the switch blades 12 and 13 and thereby maintain the igniter 19 operative.

However, if during such time period the burner 20 is not ignited by the igniter 19, the sensor 30 has caused the heater 40 to continue to operate for a certain length of time whereby the bimetallic member 31 is heated up and thereby warped to the left to pull the latch end 35 thereof away from the surface 36 of the cam 37 whereby the natural bias of the switch blade 12 rotates the cam 37 from the position illustrated in FIG. 1 to the position illustrated in FIG. 2 so that the natural bias of the switch blades 12 and 13 hold the blades 12 and 13 in an open condition thereof to terminate the flow of current to the igniter 19 and, thus, turn off the igniter 19, until the electrical switch construction 10 is reset in a manner hereinafter described.

An ambient temperature compensating bimetal member 52 has a lower L-shaped end 53 thereof also interconnected to the flexure 33 by the same fastening member 54 that fastens the L-shaped end 32 of the bimetal latch member 31 thereto as illustrated. The upper end 55 of the bimetal member 52 has a suitable opening (not shown) passing therethrough and receiving a reduced part 56 of a threaded adjusting member 57 therein, the threaded adjusting member 57 being threaded in a threaded bore (not shown) passing through a nut 58 carried in suitable recess means 59 in the housing means 11.

The reduced portion 56 of the threaded adjusting member 57 carries a disc-like member 60 on the outer end thereof and a washer-like member 61 is loosely telescoped onto the reduced part 56 of the adjusting member 57, the member 61 being urged to the right in FIG. 1 toward the disc 60 by a compression spring 62 disposed between the slideable disc 61 and the nut 58 as illustrated. In this manner, the end 55 of the compensating bimetal member 52 is held against the disc 60 of the adjusting member 57 by the disc 61 under the force of the compression spring 62.

In this manner, rotation of the adjusting member 57 at the bifurcated end 63 thereof that projects out of the housing means 11 at an opening 64 thereof will cause axial movement of the adjusting member 57 relative to the housing means 11 and thereby adjust the position of the upper end 55 of the compensating bimetal member 52 which, through its lower end 53, will change the position of the flexure 33 and, thus, the position of the latching bimetal member 31 so that the time period required for the heater means 40 to be operating before the bimetal member 31 will move to its unlatching position relative to the cam 37 can be adjusted within the limits of the adjusting member 57.

In particular, when the threaded adjusting member 57 is threaded into the housing means 11 the flexure 33 is flexed to the right in FIG. 1 and thereby requires a longer time period for the bimetal member 31 to be heated by the heater 40 before the same will move to an unlatching position thereof. Conversely, when the threaded adjusting member 57 is rotated in a manner to move the end 55 thereof to the left in FIG. 1, the flexure 33 is likewise moved to the left and thereby requires a lesser time period for the heater means 40 to heat the bimetal member 31 to cause the same to move to an unlatching position thereof.

Similarly, the ambient temperature compensating bimetal member 52 is so constructed and arranged that as the same is heated up by an increase in the temperature in the atmosphere, the same warps in a direction that tends to move the flexure structure 33 to the right in FIG. 1 to offset the likewise heating up of the bimetal member 31 by the ambient temperature that tends to warp the bimetal member 31 to its unlatching position. Thus, the bimetal member 52 compensates for such increased ambient temperature. Conversely, a drop in ambient temperature tends to cause the bimetal member 52 to move to the left and thereby carry the flexure 33 to the left an amount equal to the amount that the decreased ambient temperature caused the bimetal member 31 to move to the right and thereby offset that additional amount of time that the heater 40 would have to heat the bimetal member 31 to overcome the decreased ambient temperature.

Therefore, it can be seen that the bimetal member 31 is ambient compensated by the bimetal member 52 and can be adjusted within limits by the adjusting member 57 so as to provide the desired time delay that is required for the heater means 40 to be operated before the bimetal member 31 will move to its unlatching position.

An actuator or reset button 65 projects out through an opening 66 formed through an outer surrounding part 70 of the housing means 11 and is carried on an end 67 of a spring member 68 that has its other end 69 fastened to the part 70 of the housing means 11. The bias of the spring member 68 is such that the same tends to maintain the spring member 68 against the undersurface 71 of the housing part 70 whereby a turned end 72 of the spring member 68 merely projects into an opening 73 formed in the housing means 11 and leading to the chamber 32 thereof. However, when the button 65 is moved downwardly by an operator pushing inwardly on the same, the end 72 of the spring member 68 is moved into the chamber 32 of the housing means 11 and engages against the cam 37 at the surface 36 thereof to pivot the cam 37in a counterclockwise direction about the shaft means 38 so that the abutment 39 thereof that engages against the spring blade 12 will bow the blade 12 to the right in the manner illustrated in FIG. 4 in an attempt to reset the switch construction should the latch member 31 be in a resetting or relatching position thereof.

Another cam member 74 is also rotatably mounted to the housing means 11 by the shaft means 38 in sideby-side relation to the cam 37 and has an abutment 75 for engaging against the other spring blade 13 in the manner illustrated in the drawings, the cam member 74 being adapted to project through a cutout 76 in the spring blade 12 in the manner illustrated in FIG. 3.

The cam member 74 has a surface 77 that is adapted to be simultaneously engaged by the end 72 of the reset spring member 68 as the same is engaging the cam 37 when the end 72 is moved downwardly by the push button in the manner illustrated in FIG. 4 whereby such movement of the actuator 65 from the unactuated condition thereof of FIG. 2 to the actuated condition thereof of FIG. 4 causes the cam members 37 and 74 to be simultaneously engaged and rotate in unison in a counterclockwise direction so that the ends 39 and thereof will simultaneously move the switch blades 12 and 13 to the right while maintaining the same out of electrical contact with each other in the manner illustrated in FIG. 4. During such movement, if the latch end 35 of the bimetal member 31 is in the path of counterclockwise movement of the cam 37, the cam 37 merely cams by the same to the right to the position illustrated in FIG. 4. Upon release of the push button 65 from the acuated position illustrated in FIG. 4, both cam members 37 and 74 tend to rotate back in a clockwise direction under the natural bias of the respective switch blades 12 and 13 back to the natural condition illustrated in FIG. 2. However, if the latch member 31 has its end 35 disposed in the path of movement of the surface 36 of the cam member 37, the same will prevent the cam member 37 from being driven back in a clockwise direction so that the same will hold the switch blade 13 in its biased condition illustrated in FIG. 1 so that clockwise movement of the cam 74 will permit the switch blade 13 to move into electrical contact with the switch blade 12 in the manner illustrated in FIG. 1.

The operation of the electrical switch construction 10 of this invention in its use in the control system 18 will now be described.

Assuming that the switch construction 10 is in the latched condition illustrated in FIG. 1 wherein the cam member 37 is held by the end 35 of the latch member 31 from being rotated in a clockwise direction by the natural bias of the spring blade 12, the spring blades 12 and 13 are electrically interconnected together at the contact means 16 and 17 thereof. Thus, an electrical circuit is adapted to be provided from the power source L1 through the igniter 19 to the ground when the control device 21 is moved to an on position to close the main switch 22 as previously described.

Thus, when the operator desires to turn on the burner means 20, the operator turns the control device 21 to the on position thereof to close the main switch 22 as well as to direct fuel into the burner 20. The closing of the main switch 22 places the igniter 19 across the power source leads 24 and 26 so that the ignitor 19 is operating as the fuel issues from the main burner 20. At the same time, the sensor 30 is now placed across the power source lead 24 and ground lead 47 so that the sensor 60 permits electrical current to flow through the heater 40 to tend to heat up the latching bimetal member 31. However, the bimetal member 31 remains in its in the manner previously described.

During such time period as set by the adjusting member 57, if the igniter 19 ignites the fuel issuing from the burner 20, the sensor 30 senses the flames at the burner 20 and opens the electrical circuit therethrough to disconnect the heater 40 from the electrical power source so that the latching bimetal member 31 will remain in the condition illustrated in FIG. 1 and the switch construction will remain in its latched condition.

However, should the sensor 30 not sense flames at the burner after the lapse of the time period as set by the adjustment member 57, the heater 40 will have operated in such a manner to cause the bimetal member 31 to warp to the left and thereby move the end 35 thereof away from the surface 36 of the cam member 37 whereby the cams 37 and 74 are driven back in a clockwise direction by the natural bias of the spring blades 12 and 13 to the position illustrated in FIG. 2 to not only disconnect the heater 40 from the electrical circuit, but also to disconnect the igniter 19 therefrom.

Thereafter, should a person desire to reset the switch construction 10, that person must push inwardly on the actuator 65 from the unactuated condition thereof illustrated in FIG. 2 to the condition illustrated in FIG. 4 whereby the end 72 of the spring member 68 will act simultaneously against the surfaces 36 and 77 of the cam members 37 and 74 to rotate the same in a counterclockwise direction from the position illustrated in FIG. 2 back to the position illustrated in FIG. 4. Such movement of the earns 37 and 74 maintain the spring blades 12 and 13 out of contact with each other during such actuated movement of the actuator 65.

- A subsequent release of the actuator 65 when in its actuated condition illustrated in FIG. 4 will permit the cams 37 and 74 to be rotated back in a clockwise direction by the natural bias of the spring blades 12 and 13 if the bimetal member 31 has not cooled sufficiently to place the end 35 thereof in the path of movement of the surface 36 of the cam 37. If the bimetal member 31 has cooled sufficiently, the end 35 prevents the clockwise movement of the cam 37 so that the same remains in the position illustrated in FIG. 1 and the natural bias of the springblade 13 causes the cam 74 to move in a clockwise direction and thereby place the contact 17 thereof in electrical contact with contact 16 of the blade 12 in the manner illustrated in FIG. 1 whereby switch blades 12 and 13 will only be moved to a closed condition when the actuator 65 is released and if the latching member 31 is in a latch position thereof.

Therefore, it can be seen that this invention not only provides an improved electrical switch construction, but also this invention provides an improved electrical control system utilizing such a switch construction or the like.

While the form of the invention now preferred has been illustrated and described as required by the Patent Statutes, it is to be understood that other forms can be utilized and still come within the scope of the appended claims.

What is claimed is:

1. An electrical switch construction comprising a housing means, a pair of movable spring blades carried by said housing means and respectively having contact means normally placed out of contact with each other by the normal bias of said switch blades, 21 pair of cams rotatably carried by said housing means and being respectively engageable with said switch blades, one of said cams when in one position relative to said housing means being adapted to hold its respective switch blade into electrical contact with the other switch blade to complete an electrical circuit therebetween, the other of said cams when in one position thereof relative to said housing means being adapted to hold its respective switch blade out of contact with the other switch blade even though said one cam is in its said one position thereof to thereby prevent completion of .said electrical circuit, a movable actuator carried by said housing means and being adapted to simultaneously engage said cams and move the same to said respective one positions thereof, and latch means for holding said one cam in said one position thereof.

2. An electrical switch construction as set forth in claim 1 wherein trip means is carried by said housing means to move said latch means from its latching position with said one cam whereby the natural bias of said switch blades moves said switch blades to an open condition thereof to open said circuit.

3. An electrical switch construction as set forth in claim 2 wherein said latch means comprises a bimetal member for latching with said one cam when said bimetal member senses one certain temperature and for warping away from said one cam to unlatch therefrom when sensing another certain temperature.

4. An electrical switch construction as set forth in claim 3 wherein said trip means includes a heater means for said bimetal member to provide said other certain temperature when operated a certain amount.

5. An electrical switch construction as set forth in claim 4 wherein said trip means includes means for adjusting the same so that the amount of time said heater means is to be operated before said latch member moves to an unlatching position thereof can be selected within certain limits.

6. An electrical switch construction as set forth in claim 1 wherein said cams are rotatably carried by said housing means in side-by-side relation.

7. An electrical switch construction as set forth in claim 6 wherein said cams are rotatably mounted to said housing means by the same shaft means.

8. An electrical switch construction as set forth in claim 7 wherein said actuator must be moved from an unactuated position thereof to an actuated position thereof to move said cams to said one position thereof, said housing means having biasing means tending to always move said actuator from said actuated position thereof to said unactuated position thereof.

9. An electrical switch construction as set forth in claim 7 wherein said cams are so constructed and arranged that when said switch blades are out of contact with each other by the normal bias thereof said cams have surfaces disposed in aligned relation that are respectively engaged simultaneously by said actuator to be moved in unison by said actuator when said actuator is moved from said unactuated position thereof to said actuated position thereof whereby actuation of said actuator will not cause said switch blades to contact each other unless said latch means holds said one cam in its said one position thereof when said actuator subsequently moves back from said actuated position thereof to said unactuated position thereof.

10. An electrical switch construction as set forth in claim 9 wherein the switch blade operated by said one cam has a cut-out therethrough through which said other cam projects to engage its respective switch blade.

11. An electrical control system comprising an electrical power source, an electrically operated control device, and an electrical circuit means for interconnecting said source to said device to operate the same, said circuit means having an electrical switch construction therein, said switch construction having a housing means, a pair of movable spring switch blades carried by said housing means and respectively having contact means normally placed out of contact with each other by the normal bias of said switch blades, a pair of cams rotatably carried by said housing means and being respectively engageable with said switch blades, one of said cams when in one position relative to said housing means being adapted to hold its respective switch blade into electrical contact with the other switch blade to complete an electrical circuit therebetween whereby said source is interconnected to said control device to operate the same, the other of said cams when in one position thereof relative to said housing means being adapted to hold its respective switch blade out of contact with the other switch blade even though said one cam is in its said one position thereof whereby said electrical circuit cannot be completed when said cams are respectively in said one position thereof, a movable actuator carried by said housing means and being adapted to simultaneously engage said cams and move the same to said respective one positions thereof, and latch means for holding said one cam in said one position thereof.

12. An electrical control system as set forth in claim 11 wherein trip means is carried by said housing means to move said latch means from its latching position with said one cam whereby the natural bias of said switch blades moves said switch blades to an open condition thereof to open said circuit whereby said source is disconnected from said control device.

13. An electrical control circuit as set forth in claim 12 wherein said latch means comprises a bimetal mem ber for latching with said one cam when said bimetal member senses one certain temperature and for warping away from said one cam to unlatch therefrom when sensing another certain temperature.

14. An electrical control system as set forth in claim 13 wherein said trip means includes a heater means for said bimetal member to provide said other certain temperature when operated a certain amount.

15. An electrical control system as set forth in claim 14 wherein said trip means includes means for adjusting the same so that the amount of time said heater means is to be operated before said latch member moves to an unlatching position thereof can be selected within certain limits.

16. An electrical control system as set forth in claim 11 wherein said cams are rotatably carried by said housing means in side-by-side relation.

17. An electrical control system as set forth in claim 16 wherein said cams are rotatably mounted to said housing means by the same shaft means.

18. An electrical control system as set forth in claim 17 wherein said actuator must be moved from an unactuated position thereof to an actuated position thereof to move said cams to said one position thereof, said housing means having biasing means tending to always move said actuator from said actuated position thereof to said unactuated position thereof.

19. An electrical control system as set forth in claim 17 wherein said cams are so constructed and arranged that when said switch blades are out of contact with each other by the normal bias thereof said cams have surfaces disposed in aligned relation that are respectively engaged simultaneously by said actuator to be moved in unison by said actuator when said actuator is moved from said unactuated position thereof to said actuated position thereof whereby actuation of said actuator will not cause said switch blades to contact each other unless said latch means holds said one cam in its said one position thereof when said actuator subsequently moves back from said actuated position thereof to said unactuated position thereof.

-20. An electrical control circuit as set forth in claim 19 wherein the switch blade operated by said one cam has a cut-out therethrough through which said other cam projects to engage its respective switch blade. 

1. An electrical switch construction comprising a housing means, a pair of movable spring blades carried by said housing means and respectively having contact means normally placed out of contact with each other by the normal bias of said switch blades, a pair of cams rotatably carried by said housing means and being respectively engageable with said switch blades, one of said cams when in one position relative to said housing means being adapted to hold its respective switch blade into electrical contact with the other switch blade to complete an electrical circuit therebetween, the other of said cams when in one position thereof relative to said housing means being adapted to hold its respective switch blade out of contact with the other switch blade even though said one cam is in its said one position thereof to thereby prevent completion of said electrical circuit, a movable actuator carried by said housing means and being adapted to simultaneously engage said cams and move the same to said respective one positions thereof, and latch means for holding said one cam in said one position thereof.
 2. An electrical switch construction as set forth in claim 1 wherein trip means is carried by said housing means to move said latch means from its latching position with said one cam whereby the natural bias of said switch blades moves said switch blades to an open condition thereof to open said circuit.
 3. An electrical switch construction as set forth in claim 2 wherein said latch means comprises a bimetal member for latching with said one cam when said bimetal member senses one certain temperature and for warping away from said one cam to unlatch therefrom when sensing another certain temperature.
 4. An electrical switch construction as set forth in claim 3 wheRein said trip means includes a heater means for said bimetal member to provide said other certain temperature when operated a certain amount.
 5. An electrical switch construction as set forth in claim 4 wherein said trip means includes means for adjusting the same so that the amount of time said heater means is to be operated before said latch member moves to an unlatching position thereof can be selected within certain limits.
 6. An electrical switch construction as set forth in claim 1 wherein said cams are rotatably carried by said housing means in side-by-side relation.
 7. An electrical switch construction as set forth in claim 6 wherein said cams are rotatably mounted to said housing means by the same shaft means.
 8. An electrical switch construction as set forth in claim 7 wherein said actuator must be moved from an unactuated position thereof to an actuated position thereof to move said cams to said one position thereof, said housing means having biasing means tending to always move said actuator from said actuated position thereof to said unactuated position thereof.
 9. An electrical switch construction as set forth in claim 7 wherein said cams are so constructed and arranged that when said switch blades are out of contact with each other by the normal bias thereof said cams have surfaces disposed in aligned relation that are respectively engaged simultaneously by said actuator to be moved in unison by said actuator when said actuator is moved from said unactuated position thereof to said actuated position thereof whereby actuation of said actuator will not cause said switch blades to contact each other unless said latch means holds said one cam in its said one position thereof when said actuator subsequently moves back from said actuated position thereof to said unactuated position thereof.
 10. An electrical switch construction as set forth in claim 9 wherein the switch blade operated by said one cam has a cut-out therethrough through which said other cam projects to engage its respective switch blade.
 11. An electrical control system comprising an electrical power source, an electrically operated control device, and an electrical circuit means for interconnecting said source to said device to operate the same, said circuit means having an electrical switch construction therein, said switch construction having a housing means, a pair of movable spring switch blades carried by said housing means and respectively having contact means normally placed out of contact with each other by the normal bias of said switch blades, a pair of cams rotatably carried by said housing means and being respectively engageable with said switch blades, one of said cams when in one position relative to said housing means being adapted to hold its respective switch blade into electrical contact with the other switch blade to complete an electrical circuit therebetween whereby said source is interconnected to said control device to operate the same, the other of said cams when in one position thereof relative to said housing means being adapted to hold its respective switch blade out of contact with the other switch blade even though said one cam is in its said one position thereof whereby said electrical circuit cannot be completed when said cams are respectively in said one position thereof, a movable actuator carried by said housing means and being adapted to simultaneously engage said cams and move the same to said respective one positions thereof, and latch means for holding said one cam in said one position thereof.
 12. An electrical control system as set forth in claim 11 wherein trip means is carried by said housing means to move said latch means from its latching position with said one cam whereby the natural bias of said switch blades moves said switch blades to an open condition thereof to open said circuit whereby said source is disconnected from said control device.
 13. An electrical control circuit as set forth in claim 12 wherein said latch means compriseS a bimetal member for latching with said one cam when said bimetal member senses one certain temperature and for warping away from said one cam to unlatch therefrom when sensing another certain temperature.
 14. An electrical control system as set forth in claim 13 wherein said trip means includes a heater means for said bimetal member to provide said other certain temperature when operated a certain amount.
 15. An electrical control system as set forth in claim 14 wherein said trip means includes means for adjusting the same so that the amount of time said heater means is to be operated before said latch member moves to an unlatching position thereof can be selected within certain limits.
 16. An electrical control system as set forth in claim 11 wherein said cams are rotatably carried by said housing means in side-by-side relation.
 17. An electrical control system as set forth in claim 16 wherein said cams are rotatably mounted to said housing means by the same shaft means.
 18. An electrical control system as set forth in claim 17 wherein said actuator must be moved from an unactuated position thereof to an actuated position thereof to move said cams to said one position thereof, said housing means having biasing means tending to always move said actuator from said actuated position thereof to said unactuated position thereof.
 19. An electrical control system as set forth in claim 17 wherein said cams are so constructed and arranged that when said switch blades are out of contact with each other by the normal bias thereof said cams have surfaces disposed in aligned relation that are respectively engaged simultaneously by said actuator to be moved in unison by said actuator when said actuator is moved from said unactuated position thereof to said actuated position thereof whereby actuation of said actuator will not cause said switch blades to contact each other unless said latch means holds said one cam in its said one position thereof when said actuator subsequently moves back from said actuated position thereof to said unactuated position thereof.
 20. An electrical control circuit as set forth in claim 19 wherein the switch blade operated by said one cam has a cut-out therethrough through which said other cam projects to engage its respective switch blade. 